Remove mp_obj_type_t.methods entry and use .locals_dict instead.

Originally, .methods was used for methods in a ROM class, and
locals_dict for methods in a user-created class.  That distinction is
unnecessary, and we can use locals_dict for ROM classes now that we have
ROMable maps.

This removes an entry in the bloated mp_obj_type_t struct, saving a word
for each ROM object and each RAM object.  ROM objects that have a
methods table (now a locals_dict) need an extra word in total (removed
the methods pointer (1 word), no longer need the sentinel (2 words), but
now need an mp_obj_dict_t wrapper (4 words)).  But RAM objects save a
word because they never used the methods entry.

Overall the ROM usage is down by a few hundred bytes, and RAM usage is
down 1 word per user-defined type/class.

There is less code (no need to check 2 tables), and now consistent with
the way ROM modules have their tables initialised.

Efficiency is very close to equivaluent.

1 files changed, 9 insertions, 7 deletions

diff --git a/stmhal/usart.c b/stmhal/usart.c
index d3a54f9d84..daf8a9e1fc 100644
--- a/stmhal/usart.c
+++ b/stmhal/usart.c
@@ -8,6 +8,7 @@
 #include "mpconfig.h"
 #include "qstr.h"
 #include "obj.h"
+#include "map.h"
 #include "usart.h"
 
 struct _pyb_usart_obj_t {
@@ -209,18 +210,19 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_1(usart_obj_rx_char_obj, usart_obj_rx_char);
 STATIC MP_DEFINE_CONST_FUN_OBJ_2(usart_obj_tx_char_obj, usart_obj_tx_char);
 STATIC MP_DEFINE_CONST_FUN_OBJ_2(usart_obj_tx_str_obj, usart_obj_tx_str);
 
-STATIC const mp_method_t usart_methods[] = {
-    { MP_QSTR_status, &usart_obj_status_obj },
-    { MP_QSTR_recv_chr, &usart_obj_rx_char_obj },
-    { MP_QSTR_send_chr, &usart_obj_tx_char_obj },
-    { MP_QSTR_send, &usart_obj_tx_str_obj },
-    { MP_QSTR_NULL, NULL },
+STATIC const mp_map_elem_t usart_locals_dict_table[] = {
+    { MP_OBJ_NEW_QSTR(MP_QSTR_status), (mp_obj_t)&usart_obj_status_obj },
+    { MP_OBJ_NEW_QSTR(MP_QSTR_recv_chr), (mp_obj_t)&usart_obj_rx_char_obj },
+    { MP_OBJ_NEW_QSTR(MP_QSTR_send_chr), (mp_obj_t)&usart_obj_tx_char_obj },
+    { MP_OBJ_NEW_QSTR(MP_QSTR_send), (mp_obj_t)&usart_obj_tx_str_obj },
 };
 
+STATIC MP_DEFINE_CONST_DICT(usart_locals_dict, usart_locals_dict_table);
+
 const mp_obj_type_t pyb_usart_type = {
     { &mp_type_type },
     .name = MP_QSTR_Usart,
     .print = usart_obj_print,
     .make_new = usart_obj_make_new,
-    .methods = usart_methods,
+    .locals_dict = (mp_obj_t)&usart_locals_dict,
 };